This kind of similar problem should first put forward a hypothesis, then find the equivalence relationship contained in the problem according to the hypothesis, and list the equation relationship through the equivalence relationship to solve it.

For example, in this question, suppose that the sales profit of table lamps increases by X yuan, which is set as 1 10,000.

Then the price is 40+x, and the January price is 600- 10x.

The profit is (600-10x) x (40+x-30) =10000, that is, X -50x+400=0.

Solve to get x= 10 or 40. Sell 500 when x= 10, and sell 100 when x=40, and sell more.

Therefore, choose x= 10.

Price 50 yuan.